Shear walls or shear wall panels are used to resist lateral forces in a structure created, for example, by wind loads applied to the side of a structure or earthquakes. Conventional shear walls typically fall into three categories: (a) braced frames, (b) moment frames and (c) frames with structural sheathing.
In braced frames, a stud wall has braces which extend diagonally from a rim joist or plate at the top of the wall to a rim joist, plate or foundation at the bottom of the wall. The braces cross one or more of the studs and therefore requires cuts in the studs to let the bracing into the wall or finish materials which can accommodate the protruding bracing member. In order to avoid cutting the studs significantly or to minimize how far the brace protrudes from the wall, the braces are typically made of a steel strip or rod or a thin wooden board. Since the bracing member is longer than the wall studs, the slenderness of the bracing member limits its compressive strength and so the bracing members are installed in pairs slanting in opposite directions to provide a tensile member to resist lateral forces in either direction. In addition to these shortcomings, the braces typically occupy significant lengths of the walls which are then unavailable for windows.
In moment frames, various corners between studs and plates or joists are reinforced, typically with triangular steel plates or wooden knees. With the corners reinforced, lateral movement is resisted by moment in the studs which must bend before one of their ends can be displaced laterally while remaining vertical. This method may be suitable for timber frame or large I-beam structures in which the studs have large cross sections, but is inefficient when applied to light framing using "2 by" lumber or light metal channels. In these applications, the studs have limited moment resistance and large numbers of stud to plate or joist connections must be reinforced.
In frames with structural sheathing, plywood or oriented strand board is nailed to the studs and any sills, headers etc. used to frame openings. The sheathing panels are resistant to lateral deformation. When properly attached to the wall, the sheathing panels transfer this resistance to the wall primarily as a shear force around the perimeter of the sheathing panel. To resist this shear force, a concentrated nailing pattern is required around the perimeter of the sheathing panel. Any openings for windows require more intensive nailing and yet still weaken the panel such that some building codes deem sections of the wall with openings to have no lateral resistance. The process is time consuming and heavily dependant on quality workmanship. Further, in recent years it has been discovered that the tightly nailed sheathing panels in combination with an interior vapour barrier trap moisture within the wall which often leads to fungus growth and premature failure of the wall.